The ornamental design for a plungerunit, as shown and described.
2. Plunger unit
2.1 : Front
2.2 : Back
2.3 : Top
2.4 : Bottom
2.5 : Right
2.6 : Left
2.7 : Perspective
The broken lines shown in the drawings represent portions of the plunger unit that form no part of the claimed design. Fig.2.1 is a front view of the plunger unit; fig.2.2 is a back view thereof; fig.2.3 is a top view thereof; fig.2.4 is a bottom view thereof; fig.2.5 is a right view thereof; fig.2.6 is a left view thereof; and fig.2.7 is a perspective view thereof.